Fractionation and reconstitution of wheat flour - Effect on dough rheology and baking

A method for the fractionation and reconstitution of wheat flour, which makes it possible to investigate the contribution of flour fractions to baking performance and dough rheology, is presented. Micro-scale rheological methods and a micro-scale baking test on the basis of 10 g flour were used. Two wheat cultivars with different baking performances were studied. Fractionation involved defatting of flour by dichloromethane, formation of a dough, isolation of gluten by washing the dough with distilled water in a glutomatic at 15°C, collection of the aqueous suspension and separation into a soluble fraction and two starch fractions (upper and lower layer) by centrifugation. Reconstitution of flour gave reproducible results. The baking volumes of the reconstituted flours decreased by a factor of 0.95, and the respective doughs and glutens had higher resistances than the native flours. Mixing of reconstituted flour in the presence of reduced glutathione (0-150 nmol g ^-1) decreased the dough resistance but the native values could not be established. An increase of the total protein content of the reconstituted flour (8-16 g 100 g^-1 flour) was proportional to the baking volume. Increasing amounts of the soluble fraction led to more extensible, weaker doughs. Gliadin and glutenin had a weakening and a strengthening effect on the dough, respectively. The addition of reoxidised high molecular weight (HMW) subunits of glutenin caused an increase in dough extensibility and resistance, whereas with reoxidised low molecular weight (LMW) subunits of glutenin, only the dough resistance was increased. Micro-scale baking tests showed that HMW subunits increased the loaf volume strongly, while the opposite effect was observed for the addition of LMW subunits. Interchange of fractions between the two wheat cultivars showed that gluten was most important for the baking performance, followed by the starch and the soluble fractions.